Created attachment 135603[details]
Incorrect rendering screenshot
Mesa fails SynMark render validation for OglGSCloth test on SNB:
./synmark2 OglGSCoth
Rendering is obviously incorrect (see the the attachment). Francesco's recent GEN6-7 Transform feedback optimization patch series seems to make this somewhat worse.
I don't know whether Mesa has ever rendered it correctly on SNB, the issue has been there at least a year. Rendering is fine on GEN7+ (also with Francesco's patch series).
Unlike most of the other tests we run regularly (which work fine), GSCloth uses geometry shaders, streamout and transform feedback. GfxBench Manhattan uses also transform feedback, but that at least didn't have obvious rendering issues on SNB like this test.

Created attachment 143034[details]
Screenshot of incorrect rendering
Added screenshot from latest Mesa git version. Output is now marginally better than year ago (all content is now in correct location), but still clearly broken.
PS. Not really related to this bug, but on SNB SynMark OglTerrain*Inst tests fail to:
"Cannot allocate memory for terrain data, need 1216 layers, available 512"